Overview Of Environmental Durability Coatings And Test .
Overview of Environmental DurabilityCoatings and Test CapabilitiesCraig RobinsonGRC Materials Divisionraymond.robinson-1@nasa.gov; (216)433-5590Hypersonic Propulsion Materials and Structures WorkshopNASA Glenn Research CenterMay 1-3, 20191
Outline Environmental Effects and Coatings Branch (LME) Analytical and experimental capabilities Much more than just coatings Case Studies - Past Hypersonics related work Space Shuttle RCC Consultant 3000 F Coating for C/SiC Leading Edge Current capabilities relevant for future Hypersonics work Multi-layer Coatings Concept Unique Testing Capabilities2
NASA Environmental Effects & CoatingsCompatibility&StabilityCoatings Development Chemistries and ArchitecturesAdvanced ProcessingFailure Mechanisms / Degradation ModesEnvironmental Durability & LifingProof of Concept&Down-selectFundamental Thermo-Chemistry High Temperature Behavior Thermodynamics & Kinetics Experimental Techniques TGA Mass Spec DSC Drop CalorimetryThermodynamic&Chemistry DataExtreme Environments Testing Oxidation / CorrosionCombined thermal-mechanicalErosion / FOD / ImpactContaminants (CMAS)Computational Modeling Physics-based / Multi-scale First Principles (DFT), CALPHAD,and Empirical Utilize Machine Learning &Artificial Intelligence Database DevelopmentEmpirical Data&Model Validation3
High Temperature Thermo-Chemistry Degradation modes, kinetic rates, andthermodynamic data measurements World Class Mass Spectroscopy (2) Knudsen Effusion Mass SpectrometersHigh Pressure Mass Spectrometer Thermogravimetric Analysis, DifferentialScanning and Drop Solution Calorimetry Hi Temp X-ray Diffraction, Energy Dispersionand Raman Spectroscopy Soup-to-nuts characterizationInstrumentMeasurementsMass Spec(2000 C)Products, activities, vapor pressure,enthalpy of vaporizationTGA (1650 C air,3000 C vacuum)Wt. change, oxidation, reduction,vaporizationDSC (2400 C)Enthalpy of fusion, heat capacityDrop CalorimeterEnthalpy of formation, reaction, andmixingXRD, EDS, Raman(1600 C)Crystal structure, phase,composition, bondingExample Key Contribution:KEMSThermo-gravimetric CalorimeterAnalysis (air/water/vacuum)GRC identified Si(OH)4 product for reaction of SiCwith moisture – reaction is life limiting to SiC/SiCdurability in turbine engines4
Computational ModelingThermodynamic codes and ab initio (First Principles) calculationsAb inito (First Principles) atomistic materials modeling Density Function Theory (DFT) using VASP Kinetic Monte Carlo and Molecular Dynamics analyses Migration barrier energies, geometry optimizationEqn. of State calculations (bulk modulus, density, equilibrium)Phonon calculations (free energy, H, S, Cp, k)O2/H2O diffusivityYb2Si2O7DFT-derived data augments experimental data andimported into thermodynamic codes and CALPHADmodelsOxygen DiffusivityCALPHAD - CALculation of PHAse Diagrams Computer Coupling of Phase Diagrams and Thermochemistry Phase Diagram optimization for Rapid Materials Discovery Thermodynamic logic infers between compounds Databases needed containing boundaries & thermodynamic data fromGRC’s experimental measurements & ab initio calculations Factsage, Thermo-Calc (includes Dictra & Prism), and Pandat Examples: phase diagrams/databases for Rare Earth oxides& silicates, diffusion studies, phase and chemistry stability5
NASA EBC History 1990’s: Gen 1 (w/ GE & PW) Silicon Bond coatMullite / Mullite BSAS interlayersBSAS top coat 2000’s: Gen 2.0 Silicon bond coatRare earth (RE) silicate top coat EBC Topcoat provides barrier from turbineenvironment (H2O/CMAS) Bond Coat provides bonding / oxidationresistance Intrinsic Material Selection Criteria CTE matchPhase stability throughout thermal cycleChemical compatibilityCrack resistanceLow modulus & sinteringErosion & impact toughnessimproves H2O resistance Si bond coat limits CMC/EBC interfacetemperature (Tmelt 2400 F / 1416 C) 2010’s: Next Generation EBCs 2700oF bond coat, CMAS resistance, novel processing SlurryCMAS: calcium-magnesium-aluminum-silicon oxidesSlurry: non line-of-sight, material & chemistry flexiblePS-PVD: non line-of-sight, hybrid , microstructureflexiblePS-PVDHypersonics coatings will have different andunique requirements, but approach tomaterials properties and selection are thesame.6
Extreme Environments TestingMaterials evaluated in relevant conditions for various failure modesFacilityFailure ModesHigh Heat Flux Lasers3500-4000WCombined thermal-mechanical stressMach 0.3 Burner RigsTgas 3000 F (1648 C)Tsrf 2700 F (1482 ionThermo-mechanicalErosion/FODCMASMach 0.3Dedicated Erosion Burner RigsAdapted for CMAS compositionsErosion/FODCMASSteam Cyclic Oxidation Testing90% H2O, 2700 F (1482 C)RecessionOxidationErosionCMASQuick Access Rocket Exhaust(QARE) RigHigh temp, heat flux, velocityAlso incorporates n/FODCMASQARESteamNeed combinationof rigs toinvestigatesynergies betweenfailure modes.7
Consultants on RCC for Shuttle Orbiter 1995-2011SealantSiCCarbon/CarbonTasks: RCC Durability Developed model for oxidation through coating cracksUnderstand behavior of sealantsDeveloped characterization techniques with GRC’s ASG GroupUnderstand processing issues and coating adherence (Tiger Team)Studies on repair materials (Tiger Team)Contributions to accident investigation Establish RCC breach location, sequence, timeline8
Shuttle Orbiter ContributionsCoating Sealant behaviorSiCSiCModeling of Oxidation throughcoating cracksSiCCarbon/CarbonAir Understand effectiveness of sealant Viscosity and velocity effectsExpressions for COand CO2 fluxesdeveloped to describecavity growth Model sealant loss Expressions for vaporization9
2010 C/SiC Work - ChallengeNASA Fundamental Aero Pgm / Hypersonics Project C/SiC 3000 F Leading Edge Coating TaskOxidation protection for various regimes 1727 1327 1127927727527Protect carbon fibers from oxidation at low temps whencracks are open Temperature (C)Seal cracks in SiC seal coatProtect SiC from active oxidation at high temps and lowpressurestensileloadingCoating Concept: Leading Edge EBC Sealant Glass over C/SiC Primary oxygen barrier topcoat Viscosity to seal cracks in coating over temp rangeLow oxygen diffusivity to limit active oxidation of SiCModel oxygen diffusivity in coatingGlass sealantO2Primary oxygen barrierSiCC/SiCOxidation rates determined in airSource: Fritze et al, J. Eur. Ceram. Soc. 18 (1998)2351-2364SiC seal coat with cracks10
2010 C/SiC Work - AccomplishmentsCoating Development Degradation mechanisms identified: C fiber burnout ( 1000 C) andactive oxidation of SiC ( 1500 C, low PO2) Potential sealants identified: Na-silicate, CAS, MAS, evaluated forboth mechanisms GE1746-02-001-20Stable oxygen barriers (HfSiO4, Y2Si2O7) identified Negligible wt. change & sealcoat / topcoat compatibility SiO2 scale investigated as a barrier to active oxidation Delayed onset of active oxidation from 2-16 hours2 mmFundamental Understanding Passive-to-active oxidation investigated for SiC, C/SiC, and C-rich SiCModeling A 2-D oxygen diffusion model for coatings with cracks developed. Effect of crack width on transportEffect of relative diffusivity in crack vs bulkNext Steps: create multi-layers systems to evaluate; fundamentalunderstanding of crystallinity, impurities, O2/Ar transition points;combine diffusion & oxidation models, 3D.11
Hypersonics LE Coatings RequirementsVery different than traditional EBCsRequirements:ErosionResistanceLow OxygenPermeability High Temp / Heat Flux Oxidation ResistanceLowVolatility Shape l shockResistanceMechanical & ShockWave Load ResistanceCoatingC/CChemicalCompatibilityAdherence Like EBCs, no single material can meet all the requirements Multilayer coatings are a promising approach / architecture Multilayer coatings have shown success for EBCs Bond layer oxygen layer seal-healing layer ablation-resistant layer Key is to define & evaluate failure modes for each layer then integrate12
Multi-layer Coatings ConceptUTHCs, Silicate glasses, and SiC technologies all part of SOA. Key is to successfullyintegrate the various layers and add EBCs for oxidation.Ablation protectionUHTC-BasedEBC crack healingSilicate Glass-BasedOxidation protectionBondingEBC-BasedHfB2, HfC, ZrB2, etc. additivesSiO2 additivesSilicates additivesSiCC/C Multilayer coatings approach to individually address all coating requirements Technology for each layer exists, but no coatings technology combining all fourtechnologies exist Leverages NASA’s expertise in EBCs, slurry process, high temperature materialschemistry, and environmental testing13
High Heat Flux Laser Facility – Suite of (3) LasersSpecifications Laser Heating (3500-4000W)Button Heat fluxes 300-500 W/cm2 (265-440 Btu/ft2sec) 1650W max w/ focused spot size Backside air cooling Surface Temperature:thermal stresses Multi-λ pyrometers and IR Camera Surface Temperatures over 3100 F (1700 C) arematerial dependentAirfoilL.E. Combined thermal-mechanical load Multi-axis loadingIn-plane and thru thickness strainsConfigurations(HO)(H2O)SPLCF Button, dog-bone, leading edgeor airfoil geometries CMC, EBC, SiC, Si3N4 Isothermal, thermal gradient,steady-state, cyclic capability Tensile, flexural, fatigue, creep,thermal conductivityButton14
Quick Access Rocket Exposure (QARE) RigAtmospheric rig for testing in high heat flux oxidation environments for evaluating combinedthermal-mechanical-environmental failure modesSpecifications: QARE I recently replaced w/ QARE II Continuous supply of natural gas & 93% Oxygen 1-1.5” dia. flame (3 nozzle sizes) Estimated 4200 F (2325 C) Tflame 3100 F (1700 C) Tsurface HF 230 W/cm2 (200 Btu/ft2-sec) for ¼” cylinderQARE I Also provides 58% H2O for recession Higher volatility than Jet A burner rigs and Lasers Pre-Arc Jet Test Screening Over 1M investment to dateQARE IQARE II Configurations: Coupon, airfoil, leading edge geometries RCC, GRCop84, NiAl, various coatings Surface Temperature: Pyrometers and IR Camera Active cooling availableQARE II Cooled heat flux sensors, GRCop84 panels Static load frame available15
Summary Recap LME’s Capabilities: We understand the environments & degradation modes Fundamental high temperature thermo-chemistry In-house processing of coatings Slurry & PS-PVD We have extensive experience developing & testing materials underextreme conditons Past related contributions can serve as jump-off point Oxidation modeling & sealants 30 yrs SiC and EBC expertise Characterization Ready for immediate contributions Multilayer coating architectures Unique test capabilities QARE Rig Lasers Please join our tours this afternoon interested16
Environmental Effects and Coatings Branch (LME) Analytical and experimental capabilities Much more than just coatings Case Studies - Past Hypersonics related work Space Shuttle RCC Consultant 3000 F Coating for C/SiC Leading Edge Current capabilities relevant f
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Thermal Barrier Coatings, as the name suggests are coatings which provide a barrier to the flow of heat. Thermal Barrier Coatings (TBC) performs the important function of insulating components such as gas turbine and aero engine parts operating at elevated temperatures. Thermal barrier coatings (TBC) are layer systems deposited on
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Protective Coatings 'If the surface preparation isn't correct, the best coating in the world will not protect the steel.' Protective coatings are the most common form of corrosion control. High performance coatings can give very high durability steel structures if applied to properly prepared surfaces.
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